6.82.

A mineral containing 90% by weight of MgSO7H,0 and the balance of insoluble minerals is fed to a dissolution tank at a rate of 60,000 Ibm/h along with fresh water and a recirculation stream. The contents of the tank are heated to 110F. causing all the magnesium sulfate heptahydrate of the mineral to dissolve and form a saturated solution. The resulting sludge of minerals insoluble in a saturated solution of MgSO is pumped into a hot filter, where the wet filtration cake is separated from a solid-free filtration. The filtration cake retains 5 Ibm of solution saturated by 100 Ibm of minerals. The filtration is sent to a crystalizer, where the temperature is reduced to 50F, generating a sludge of MgSO 7H20 crystals in a saturated solution that is sent to another filter. The filtration cake produced contains all the crystals and the solution trapped in them. Again in the ratio of 5 Ibm of solution per 100 Ibm of crystals. The filtering of this filter is returned to the

Dissolution tank as a recirculation current.

Solubility data: saturated solutions of magnesium sulfate at 110F and 50F contain

32% by weight of MgSO; and 23% by weight of MgSO, respectively.